This invention is directed to improved superplastic aluminum alloys and process for forming improved superplastic aluminum alloys. The improved alloys and processes are utilized alone, together or further with cavity suppression during superplastic forming of component parts.
Superplastic forming initially utilized for titanium alloys has recently been adapted for use on aluminum alloys. Since high strength aluminum alloys are used extensively in airframes the application of superplastic forming technology to aluminum alloys is expected to be very beneficial for aircraft construction.
Initial explorations of superplastic forming of aluminum alloys have resulted in certain thermomechanical treatments which have yielded improvments in the microstructure of certain off the shelf conventional aluminum alloys. This has resulted in aluminum alloys having decreased flow stress, high m values and large elongations at reasonable strain rates. A method of producing superplastic aluminum alloy sheets having improved properties is disclosed in U.S. Pat. No. 4,486,244 to Ward et al.
As opposed to titanium alloys, aluminum alloys are susceptible to cavitation during superplastic forming. U.S. Pat. No. 4,516,419 to Agrawal describes a method of controlling cavitation during superplastic forming by utilizing differential pressure between a cap side and a cavity side of a die utilized in the superplastic forming process.
While both of the above processes have led to improvements in properties of the superplastic aluminum alloys or improvements in control of the superplastic forming process, because of the large potential scale of use of superplastic forming of aluminum alloys further improvements are deemed necessary to improve both the alloys and the forming processes such that greater material properties can be achieved and/or better controlled forming processing can be practiced to increase yields, reduce costs and/or to increase the inherent properties of the components produced utilizing superplastic forming technology.